Definition

• Infection of the interior surface of the heart, usually a heart valve.

Classification

• Acute endocarditis is caused by pathogenic organisms infecting a structurally normal heart.

• Subacute endocarditis is a more insidious illness caused by weakly pathogenic organisms infecting a structurally abnormal heart.

Epidemiology

• Uncommon, but important to recognize.

Microbiology

• Acute endocarditis is usually due to Staphylococcus aureus.

• Subacute endocarditis is most commonly due to Streptococcus viridans or enterococci.

Pathogenesis

• S. aureus usually gains access to the blood from the skin via indwelling vascular lines or via intravenous drug abuse.

• S. viridans gains access to the blood from the oropharynx after tooth brushing or dentistry.

• enterococci gain access to the blood following instrumentation of the bowel or bladder.

Presentation

 • left- sided acute endocarditis presents acutely with fever and signs of valve damage. Major systemic embolic events are also common with septic emboli travelling to multiple organs.

• Right- sided acute endocarditis presents with fevers, chills, and prominent pulmonary symptoms due to numerous septic emboli in the lungs. • Subacute endocarditis causes low- grade fever and constitutional symptoms. the diagnosis may be difficult and easily overlooked.

Macroscopy

• the involved endocardial surface is covered with friable vegetations (Fig. 4.2).

• Acute cases may show extensive underlying tissue destruction and abscess formation

Histopathology

• Vegetations are composed of a mixture of fibrin, inflammatory cells, and bacterial colonies which are usually Gram- positive cocci.

Prognosis

• Acute endocarditis has a high mortality due to rapid valve destruction and the development of acute cardiac failure.

• Subacute endocarditis has a more protracted course but remains a serious disease if undiagnosed and untreated